Air pumping jet system



May 24, 1955 F. A. CARPENTER 2,708,881

AIR PUMPING JET SYSTEM Filed Nov. 24, 1952 2 Sheets-Sheet l F250 CQ/QPENTEE INVENTOR.

May 24, 1955 Filed Nov. 24, 1952 F. A. CARPENTER AIR PUMPING JET SYSTEM 2- Sheets-Sheet 2 ihgypw PUMP F950 4, CfiQPA'A TEE IN VEN TOR.

QTTQPNEVS nited States PatentO AIR PUMPING JET SYSTEM Fred A. Carpenter, Berkeley, Calif., assignor to Berkeley Pump Company, Berkeley, Calif., a corporation of California Application November 24, 1952, Serial No. 322,245

3 Claims. (Cl. 103-6) This invention relates to a pumping system, and particularly to a pumping system of the type including a water storage tank adapted to be supplied with water under pressure by a pump and which tank is partially filled with air under pressure so that water under approximately pump pressure is available at all times even though the pump operates intermittently. In such a system, air unavoidably leaks out,'and must be replaced, or the tank becomes water-logged, i. e., there exists toogreat a ratio of water to air and hence the pressure in the tank drops rapidly to a low unsatisfactory value during the initial period of withdrawal of water from the tank.

A main object of the present invention is to provide an improved system of the above type, and in particular to provide in such a system a novel arrangement for assuring adequate replacement of lost air to prevent waterlogging of the tank.

Another object of the present invention is to provide an improved system of the above general type arranged so that water can be delivered directly from the pump to the outlet of the system without passing through the tank.

In such a system, a pressure control device is mounted on the tank and operates to de-energize the pump motor when the tank pressure attains a predetermined value, and to energize the motor when the pressure falls below a second and lower predetermined value. It is desirable to have a pump with considerable capacity and yet, not infrequently, short cycling of the pump motor occurs because after the withdrawal of'a small amount of water, the pump operates to build the pressure back up to a value to cut off the pump motor before the motor has attained full speed. Since the motor before attaining full speed draws very high current, the pressure switch or switches, conventionally provided in the current supply lines to the pump motor, are eventually damaged because of arcing between the switch contacts.

A further object of the present invention is to provide a system of the above general type in which short cycling of the pump motor is avoided, yet in which a pump is provided having considerable capacity and in which the actual capacity of the pump is available at the outlet, although the effective capacity of the pump relative to the tank is lower than the actual capacity of said pump. Specifically, it is an object of the present invention to provide a relatively restricted passageway between the pump and the tank for preventing a too sudden build up of the pressure in the tank after withdrawal of water therefrom so that cut-off of the pump motor occurs after it has attained maximum speed, at which time a relatively low current is drawn and, therefore, damage to the pressure switch or switches is avoided.

A still further object of the present invention is to provide a system of the type referred to in the above paragraph wherein there is a relatively unrestricted outlet passage communicating with the tank and with the outlet of the system and by-passing the restricted passageway, and wherein such outlet passage is closed by a check valve opening outwardly with respect to the tank.

2,708,881 Patented May 24, 1955 'ice Various other objects of the present invention will be apparent from the following description taken in connection with the accompanying drawings wherein:

Fig. l is an elevational view of a system embodying the the concepts of the present invention, some of the parts being shown in section.

Fig. 2 is a top view of the syetem disclosed in Fig. 1.

Fig. 3 is a sectional view taken along line 3-3 of Fig. 1.

Referring to the accompanying drawings wherein similar reference characters designate similar parts throughout, there is disclosed a Water storage pressure tank 11 having connected thereto adjacent its lower end a tubular member 13 serving both as an outlet and an inlet connection for the tank. Connected to tubular member 13 is a T 15 which is in turn connected to a pump 17. Also connected to T 15 is an outlet pipe 18.

Pump 17 may be located adjacent to tank 11 or spaced some distance therefrom, and may be of any suitable design, but preferably is of the variable capacity type, such as, for instance, a centrifugal jet or deep well turbone type of pump. Such a pump is driven by an electric motor, normally of the induction type.

Tubular member 13 has formed internally thereof a depending boss 19 in which is fitted a venturi tube 21 comprising two pieces 23 and 25 shouldered against the opposite sides of boss 19 and spaced apart at their adjacent ends at 26, which adjacent ends form the throat of the venturi tube. An outwardly opening check valve 27 is slidably mounted on tubular portion 23 and spring urged by a spring 29 into seating engagement with boss 19 and a rib 31, forming an annular continuation of boss 19, to direct the flow of fluid from pump 17 to the tank 11 through the venturi tube 21. Check Valve 27 is unseated when the pressure in the T drops below the tank pressure, as occurs when an outlet control valve, not shown, but which controls the flow of water from outlet pipe 18, is opened.

Boss 19 is provided with a threaded bore 33 communicating with space 26 and threadedly receiving a nipple 35. Extending from nipple 35 and connected thereto is a conduit 37 provided at its opposite end with a nipple 39, the latter threadedly fitting within a bore 41formed in a valve body 43 of an air control valve generally entitled 55. Valve body 43 isconnected to and supported from.

tank 11 by means of a pipe section 46. Formed in the lower part of valve body 43 is a countersunk bore 49communicating with bore 41 and containing a spring-pressed ball check valve 51 normally seating against acentrally apertured cap 53 threaded onto the body. A suitable annular gasket 55 is disposed between the cap and the body.

Formed in the upper portion of valve body 43 is a threaded bore 57 communicating with pipe section 46, with a pressure gauge 59 threaded into said bore, and with bore 41 through a restricted passageway 61.

Mounted on tank 11 at the upper end thereof is a pressure control device. generally entitled 63 which is connected to the pump motor so as to de-energize the same when the tank pressure attains a predetermined value, and to energize the pump motor when the tank pressure falls below a second and lower predetermined value.

I The operation of the device is as follows: It can be assumed that the water level is at point A, which is the normal level of the water when the pump has just been de-energized and the. system is operating in a normal fashion, there being such a quantity of air in the tank that the compression or confinement of the same in the space above point A in the tank results in a pressure suflicient-to operate pressure control device 63 tode-energize the pump motor. It may now be assumed that water is withdrawn from the tank, check valve 27 opening because of the differential pressure thereacross to allow outward flow of water from the tank at approximately pump capacity through the U-shaped opening provided between boss 19 and rib 31, water also passing through the venturi tube 21, but not withdrawing air through conduit 37 because with the checkvalve open there is substantially no drop in pressure at space 26. The water level descends to say point B and the air pressure consequently decreases to a value where control 63 causes energization of the pump motor so the pump is operated to supply water to the T, closing the check valve and supplying make-up water to the tank through the venturi tube. A low pressure at here 26 (at the throat of the venturi) is created so as to circulate air from the top of the tank through orifice 61, conduit 37, the venturi tube and then upwardly through the water in the tank to the top of the tank. Suificient air can be drawn through orifice 61 to prevent the creation of a sub-atmospheric pressure at bore 41 so that check valve 51 remains closed.

As water level rises during the operation of the pump, the air in the tank is compressed back to its original pressure (at which time the water has reached point A), and hence pressure control device 63 operates to de-energize the pump motor.

As the above cycle of operation continues, air will be unavoidably lost for reasons well known to those skilled in the art and the water level will consequently rise beyond point A before it compresses the now smaller quantity of air to a pressure sufficient to actuate pressure control device 63. It may be assumed that the water rises to point C before the pressure control device 63 is actuated. During the rise of the water level from point A to point C, water will flow into pipe section 46 and into orifice 61. Now, water instead of air is drawn through orifice 61. Water, being a much more viscous fluid than air, can be drawn through the orifice only at a slower rate and hence the pressure at 41 falls below atmospheric so that check valve 51 opens to admit air into the system. During subsequent cycles of operation additional quantities of air are drawn in until the water level again drops to point A (at which level there is now suflicient air within the tank that when confined within the space above level A, the pump cut-oif pressure of control 63 is attained).

The above explanation has been based on the premise that a subatmospheric pressure is created in 41 any time the pump is pushing water through venturi 21 and the water level is at point A or higher so that water is present in orifice 61. In actual practice, it has been found that a subatmospheric pressure is created in bore 41 only when the differential pressure between T 15 and the tank exceeds a certain value (and, when, of course, water is present in orifice 61). The actual value, as contrasted with percentage value, of this critical differential pressure varies with the pressure in the tank and in the T. In some conventional installations, the T pressure must he at least 150% of the tank pressure in order to attain a sub-atmospheric pressure in bore 41 (of course assuming the presence of water in orifice 61).

Since it is contemplated that a variable capacity pump will be utilized, the maximum differential pressure will occur just when the pump is cut in, because as the tank pressure rises, the pump pressure in the T rises but at a lower rate so that the differential pressure drops. It follows that in many installations the cut-off ditferential pressure will not be sufficient to create a subatmospheric pressure in 41 (with water in 61). Thus, the cut-01f water level may be at point C or higher, whereas the cut-in water level may rise to pipe 46 depending on the characteristics of the installation. For instance, if the arrangement is such that sufficient differential pressure to create a subatmospheric condition at bore 41 (with water in 61) exists only during the very first part of the period of operation of the pump, then that is the only time additional air could be drawn in through valve 51, and hence the cutin water level would rise until water was present in orifice 61 during the very first part of the period of operation of the pump. If sufficient differential pressure (to create a subatmospheric pressure at 41 with water in 61) exists during a longer first part of the period of operation of the pump, the cut-in water level will drop commensurately somewhat below pipe 46.

It is apparent from the above description that a novel system has been provided for preventing water-logging of a pressure tank, which system allows the pump to be located a considerable distance from the tank, since the only connections to the pump are the supply line from the pump to the T and wiring from control device 63 to the pump motor. It is also apparent that with the above system provision is made for delivering water at the actual pressure and capacity of the pump at the outlet of the system. Further, the danger of short cycling is substantially eliminated since a restricted passageway is interposed between the pump and the tank so that after a small quantity of water is withdrawn from the tank (through a passage by-passing the restricted passageway) there can be no immediate build up of the pressure in the tank since the full capacity of the pump is not available to the interior of the tank for such an immediate build up.

While I have shown the preferred form of my invention, it is to be understood that various changes may be made in its construction by those skilled in the art without departing from the spirit of the invention as defined in the appended claims.

Having thus described my invention, what I claim and desire to secure by Letters Patent is:

l. A device of the class described, comprising a pressure tank having connected thereto at the lower portion thereof a conduit functioning both as an outlet from and an inlet to the tank, said conduit having an inlet separate from its outlet adapted to be connected to a pump to provide for the supply of water to the tank, a venturi tube mounted centrally in said conduit located inwardly of the conduit inlet, an outwardly facing valve seat in said conduit adjacent the midpoint of said venturi tube, an outwardly opening annular check valve slidably mounted on the outer end of said venturi adapted to seat against said valve seat when water is being supplied to said tank by said pump forcing said water to pass through the venturi and to open to by-pass said venturi when the water is being withdrawn from said tank, means providing communication between the upper portion of the tank and the venturi tube, said means including an outwardly urged inwardly opening check valve for admitting air into said means when the pressure on the inner side of said valve drops below a predetermined value, and a pressure control device communicating with the tank for inactivating the pump when the pressure in the tank reaches a predetermined value, said means also including a restricted passage therein located at a place between the location of the check valve and the tank, whereby waterlogging of the tank is prevented by the taking in of air by said venturi tube through said check valve when waer is being supplied to said tank at least during part of the time that the water level in the tank disposed at or above the point of communication of said means with said tank.

2. A device of the class described, comprising a pressure tank having connected thereto at the lower portion thereof a conduit functioning both as an outlet from and an inlet to the tank, said conduit having an inlet separate from its outlet adapted to be connected to a pump to provide for the supply of water to the tank, a venturi tube mounted centrally in said conduit located inwardly of the conduit inlet, an outwardly facing valve seat in said conduit adjacent the midpoint of said venturi tube. an outwardly opening annular check valve slidaoly mounted on the outer end of said venturi adapted to seat against said valve seat when water is being supplied to said tank by said pump forcing said water to pass through the venturi and to open to by-pass said venturi when water is being withdrawn from said tank, means providing communication between the upper portion of the tank and the venturi tube, said means including an outwardly urged inwardly opening check valve for admitting air into said means when the pressure on the inner side of said valve drops below a predetermined value, and a pressure control device communicating with the tank for inactivating the pump when the pressure in the tank reaches a predetermined value, said means also including a restricted passage therein located at a place between the location of the check valve and the tank, whereby water-logging of the tank is prevented by the taking in of air by said venturi tube through said check valve when Water is being supplied to said tank at least during part of the time that the water level in the tank is disposed at or above the point of communication of said means with said tank.

3. A device of the class described, comprising a pressure tank having connected thereto at the lower portion thereof a conduit functioning both as an outlet from and an inlet to the tank, a centrifugal pump connected to the conduit to deliver water thereto to supply water to the conduit outlet and/ or to the tank, a venturi tube mounted centrally in said conduit located inwardly of the conduit inlet, an outwardly facing valve seat in said conduit adjacent the midpoint of said venturi tube, an outwardly opening annular check valve slidably mounted on the outer end of said venturi adapted to seat against said valve seat when water is being supplied to said tank by said pump forcing said water to pass through the venturi and to open to by-pass said venturi when water is being withdrawn from said tank, means providing communication between the upper portion of the tank and the venturi tube, said means including an outwardly urged inwardly opening check valve for admitting air into said means when the pressure on the inner side of said valve drops below a predetermined valve, and a pressure control device communicating with the tank for inactivating the centrifugal pump when the pressure in the tank reaches a predetermined value, said means also including a restricted passage therein located at a place between the location of the check valve and the tank, whereby water-logging of the tank is prevented by the taking in of air by said venturi tube through said check valve when water is being supplied to said tank at least during part of the time that the water level in the tank is disposed at or above the point of communication of said means with said tank.

References Cited in the file of this patent UNITED STATES PATENTS 

